﻿using System;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Media.Imaging;
using System.Windows.Media;


namespace Macad.Presentation
{
    /// <summary>
    /// Class used to have an image that is able to be gray when the control is not enabled.
    /// Based on the version by Thomas LEBRUN (http://blogs.developpeur.org/tom)
    /// </summary>
    public class AutoGreyableImage : Image
    {
        /// <summary>
        /// Initializes a new instance of the <see cref="AutoGreyableImage"/> class.
        /// </summary>
        static AutoGreyableImage()
        {
            // Override the metadata of the IsEnabled and Source property.
            IsEnabledProperty.OverrideMetadata(typeof(AutoGreyableImage), new FrameworkPropertyMetadata(true, new PropertyChangedCallback(OnAutoGreyScaleImageIsEnabledPropertyChanged)));
            SourceProperty.OverrideMetadata(typeof(AutoGreyableImage), new FrameworkPropertyMetadata(null, new PropertyChangedCallback(OnAutoGreyScaleImageSourcePropertyChanged)));
        }

        protected static AutoGreyableImage GetImageWithSource(DependencyObject source)
        {
            var image = source as AutoGreyableImage;
            if (image == null)
                return null;

            if (image.Source == null)
                return null;

            return image;
        }

        /// <summary>
        /// Called when [auto grey scale image source property changed].
        /// </summary>
        /// <param name="source">The source.</param>
        /// <param name="args">The <see cref="System.Windows.DependencyPropertyChangedEventArgs"/> instance containing the event data.</param>
        protected static void OnAutoGreyScaleImageSourcePropertyChanged(DependencyObject source, DependencyPropertyChangedEventArgs args)
        {
            AutoGreyableImage image = GetImageWithSource(source);
            if (image != null)
                ApplyGreyScaleImage(image, image.IsEnabled);
        }

        /// <summary>
        /// Called when [auto grey scale image is enabled property changed].
        /// </summary>
        /// <param name="source">The source.</param>
        /// <param name="args">The <see cref="System.Windows.DependencyPropertyChangedEventArgs"/> instance containing the event data.</param>
        protected static void OnAutoGreyScaleImageIsEnabledPropertyChanged(DependencyObject source, DependencyPropertyChangedEventArgs args)
        {
            AutoGreyableImage image = GetImageWithSource(source);
            if (image != null)
            {
                var isEnabled = Convert.ToBoolean(args.NewValue);
                ApplyGreyScaleImage(image, isEnabled);
            }
        }

        protected static void ApplyGreyScaleImage(AutoGreyableImage autoGreyScaleImg, Boolean isEnabled)
        {
            try
            {
                if (!isEnabled)
                {
                    BitmapSource bitmapImage = null;

                    if (autoGreyScaleImg.Source is FormatConvertedBitmap)
                    {
                        // Already grey !
                        return;
                    }
                    else if (autoGreyScaleImg.Source is BitmapSource)
                    {
                        bitmapImage = (BitmapSource) autoGreyScaleImg.Source;
                    }
                    else // trying string 
                    {
                        bitmapImage = new BitmapImage(new Uri(autoGreyScaleImg.Source.ToString()));
                    }
                    FormatConvertedBitmap conv = new FormatConvertedBitmap(bitmapImage, PixelFormats.Gray32Float, null, 0);
                    autoGreyScaleImg.Source = conv;

                    // Create Opacity Mask for greyscale image as FormatConvertedBitmap does not keep transparency info
                    autoGreyScaleImg.OpacityMask = new ImageBrush(((FormatConvertedBitmap) autoGreyScaleImg.Source).Source); //equivalent to new ImageBrush(bitmapImage)
                }
                else
                {
                    if (autoGreyScaleImg.Source is FormatConvertedBitmap)
                    {
                        autoGreyScaleImg.Source = ((FormatConvertedBitmap) autoGreyScaleImg.Source).Source;
                    }
                    else if (autoGreyScaleImg.Source is BitmapSource)
                    {
                        // Should be full color already.
                        return;
                    }

                    // Reset the Opcity Mask
                    autoGreyScaleImg.OpacityMask = null;
                }
            }
            catch (Exception)
            {
                // nothin'
            }

        }
    }
}
